duplicate the mesh in edit mode and flip normals using python script
Then you get this error 

'NoneType' object has no attribute 'copy'


This means, that you try to get attribute from object 'NoneType'. NoneType is nothing.  So you want to get something from none. Why dup_object is None? You will get 'NoneType' when try to get object, that doesn't exists. I guess there is no object with name ""object"". Why name is "object"? - check this.